The present invention relates generally to methods and apparatuses for repositioning percutaneous probes, such as percutaneous electrodes used for electrical nerve stimulation.
Electrical therapy has long been used in medicine to treat pain and other conditions. For example, transcutaneous electrical nerve stimulation (TENS) systems deliver electrical energy through electrode patches placed on the surface of a patient""s skin to treat pain in tissue beneath and around the location of the patches. One problem with TENS systems is that they may not provide patients with adequate pain relief.
More recently, a technique in which electrodes are placed through the patient""s skin into the target tissue has been proposed. Percutaneous Neuromodulation Therapy (xe2x80x9cPNTxe2x80x9d) (also sometimes called Percutaneous Electrical Nerve Stimulation or xe2x80x9cPENSxe2x80x9d) using percutaneously placed electrodes achieves significantly better pain relief results than TENS treatments using skin surface electrodes. This therapy is described in Ghoname et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation for Low Back Pain,xe2x80x9d JAMA 281:818-23 (1999); Ghoname et al., xe2x80x9cThe Effect of Stimulus Frequency on the Analgesic Response to Percutaneous Electrical Nerve Stimulation in Patients with Chronic Low Back Pain,xe2x80x9d Anesth Analg. 88:841-6 (1999); Ahmed et al,. xe2x80x9cPercutaneous Electrical Nerve Stimulation (PENS): A Complementary Therapy for the Management of Pain Secondary to Bony Metastasis,xe2x80x9d Clinical Journal of Pain 14:320-3 (1998); and Ahmed et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation: An Alternative to Antiviral Drugs for Herpes Zoster,xe2x80x9d Anesth. Analg. 87:911-4 (1998). The contents of these references are incorporated herein by reference.
One method for applying percutaneous nerve stimulation is to insert acupuncture needles into the patient""s skin and attach the needles to waveform generators via cables and alligator clips to deliver a percutaneous electrical current. One drawback with this method is that the electrical connections to the needle may not be sufficiently secure and reliable. Another drawback with this method is that it may be difficult to accurately position the needles. For example, if a needle is placed too close to a nerve within a nerve region it is intended to treat, the needle itself may be painful and/or the amount of electrical current necessary to provide effective therapy may be painful. Accordingly, the practitioner may need to reposition the needle to a new location. However, it may be difficult for the practitioner to accurately reposition the needle. For example, the practitioner may lose track of the needle""s original position once the needle is removed. Without having the original position of the needle as a reference, the practitioner may be unable to accurately locate the new position. Furthermore, the practitioner may not be able to accurately control the angle at which the needle re-enters the skin at the new position. If the angle is different than the initial angle at which the needle entered the skin, the tip of the needle can end up at the same point it was before the repositioning process began.
The present invention is directed to methods and apparatuses for repositioning percutaneous probes. A method in accordance with one aspect of the invention includes engaging a housing coupled to the probe with a selected location on a skin surface, and inserting the probe through the skin at a first position on the surface of the skin, for example, relative to a target nerve region beneath the skin. The method can further include withdrawing the probe from the first position and reinserting the probe into the skin at a second position by moving the probe relative to the housing while the housing remains at the selected location. The method can still further include moving the probe in a first direction relative to the housing and away from the skin without moving the probe in a second direction relative to the housing and aligned with the skin. The probe can be moved relative to the housing by orbiting the probe about an axis offset from a central axis of the housing or by moving the probe along a straight line in a plane aligned with and offset from the surface of the skin.
A method in accordance with another aspect of the invention is directed to manufacturing a device for penetrating skin. The method can include fixedly positioning a probe in a slider member, disposing the slider member in a cavity of a housing, with the probe generally parallel to and offset from a major axis of the cavity, and at least restricting motion of the slider member out of the cavity by at least restricting rotational motion of the slider member in one direction relative to the housing. In a further aspect of the invention, the housing can include a first portion defining a first portion of the cavity and can be pivotably coupled to a second portion defining a second portion of the cavity. The method can further include positioning the slider member between the first and second portions of the housing and pivoting at least one of the first and second portions of the housing toward the other to receive a first part of the slider member in the first portion of the cavity and to receive a second part of the slider member in the second portion of the cavity.
The invention is also directed to an apparatus for piercing a skin surface. In one aspect of the invention, the apparatus can include a support housing having a casing defining an axial direction and an engaging surface to engage the skin surface at one end of the casing. The support housing can have a first guide extending axially away front the engaging surface and a second guide extending transverse to the first guide. The apparatus can further include a probe coupled to a guide member that is sequentially engaged with the first guide and the second guide to move in a first direction toward and away from the engaging surface without simultaneously moving in a second direction transverse to the first direction. In a further aspect of the invention, the first guide can include a first channel, the second guide can include a second channel, and the guide member can be slideably received. Sequentially in the first and second channels. The probe can be removably coupled to an, electrical contact, which is in turn connected to a current source for delivering percutaneous electrical stimulation to a recipient.